1. Field of the Invention
The present invention relates generally to footwear, and in particular a cooling system for an article of footwear.
2. Description of Related Art
Articles of footwear with ventilation systems have been proposed. In general, cooling or ventilation systems included in articles of footwear may be divided into two categories: those passively allowing air exchange and those including a mechanism for actively facilitating air exchange.
The following references teach passive systems. Moretti (U.S. Pat. No. 5,992,052) discloses a shoe with a vapor permeable insole that also includes a waterproof membrane. Polegato (U.S. Pat. No. 5,983,524) discloses a similar vapor-permeable shoe that is also water proof. Lechhart et al. (U.S. patent number 2005/0172513) disclose a breathable sole structure for footwear. The footwear sole structure includes an insole, an outsole, and a functional membrane system.
Berger et al. (U.S. Pat. No. 6,817,112) teaches an article of footwear that includes openings for ventilation and vapor exchange. The sole of Berger's design includes at least three layers. Each of the layers has one or more openings, so that ventilation and air exchange may occur within the article of footwear. The partial overlapping of these holes provides a substantially larger number of openings without reducing the mechanical stability of the shoe. Although these references teach the concept of allowing air to be transferred through the insole or a membrane in the article of footwear, there is no mechanism for facilitating the flow of air.
Articles of footwear including provisions for actively facilitating air exchange have been disclosed. Pfander (U.S. Pat. No. 6,976,319) discloses an article of footwear that includes a midsole having a front portion with a plurality of spaced holes that are vertically aligned to allow airflow through the midsole. In particular, the plurality of spaced holes are aligned with a set of moguls in the outsole for the purpose of providing air flow through the midsole when the moguls are deformed by the weight and walking action of the wearer. Generally, however, the holes in the midsole are positioned only in the forefoot region. Furthermore, the air is not channeled directly to the holes, but rather the holes are in contact with a large space, and the moguls deform within that large space. This design lacks an efficient means of circulating the air directly throughout the entirety of the midsole.
Huang (U.S. Pat. No. 5,341,581) discloses a compression cooling system of a shoe midsole comprising mainly a main body, an air sac and an air duct. During typical use, the air duct of the Huang device, which is disposed along the heel, is compressed and circulates air through the air duct. Air is transported through the air duct to an air slot and four air holes, disposed along the forefoot of the midsole. This design requires an air admitting one-way valve and an air discharging one-way valve. In addition, the air holes in the midsole are not distributed throughout the midsole, but only in the forefoot portion. The design of Huang requires a large number of components in order to achieve ventilation of the foot through the midsole and outsole and does not include holes for ventilation throughout the entirety of the midsole.
There is a need in the art for an article of footwear incorporating a simple design, eliminating the need for multiple layers and valves, and a design that simultaneously incorporates multiple holes disposed along the midsole to provide ventilation to the entire length of the article of footwear.